Sound systems installed in automotive vehicles are typically equipped with controls for adjusting tone, either by bass and treble controls or by multi-channel equalizers, to adjust the sound characteristics to the preference of the operator. Thus a certain amount of balance of frequency ranges is attained. Where the vehicle is equipped with front and rear speakers, a fade control is used to apportion the sound volume between the front and rear. When fade is changed, the balance of the frequency ranges is often changed as well, depending on the acoustical response characteristics of the vehicle. This causes the operator to adjust the bass/treble settings manually upon each fade operation to maintain a consistent sound.
To overcome drastic changes in the frequency response due to fade changing it is sometimes attempted to design a "flat" response in a given style of vehicle by redesign of speakers, the acoustical housing, electronic hardware, and speaker location. Such customizing is expensive and takes considerable time.
Present vehicle radio systems tend to use microprocessor control technology and thus have the capability of calibrating various functions by software design. It is desirable then to use software calibration rather than hardware changes to customize the frequency response of a system for a given vehicle to meet user expectations thereby achieving a new level of flexibility in audio system design at minimal or no extra expense.